1. Field of the Invention
This invention relates to a method for the manufacture of shaped articles of an organic substance.
2. Description of the Prior Art
The shaped articles produced from organic substances as raw materials find extensive utility in numerous fields. For example, shaped materials, noise absorbers, and heat insulation panels are used in automobiles, buildings, and electric appliances and cushioning materials are used for protection of various packages. The term "organic substance" as used herein means waste fibers arising from textile products such as articles of clothing, fibers arising from used paper, synthetic fibers, natural fibers, and pulp fibers. Wood flour, ground rice hulls, powdered pulp, chips, flakes, and other similar small particles are also usable as raw materials.
The methods heretofore adopted for the manufacture of shaped articles of organic substances may be broadly classified under wet methods and dry methods. A typical wet method comprises the steps of casting a pulp suspension in a metal die capable of removing water by suction, pressing the pulp suspension with a rubber pack thereby squeezing water therefrom and, at the same time, preforming the drained pulp, then drying the preformed mass of pulp by means of hot air or high frequency or compression drying the drained mass of pulp in a heated die. A typical dry method comprises blowing current of hot air through a mixture of pulp and thermoplastic resin or thermosetting resin thereby half burning the mixture and, at the same time, fleece molding it, and then completely burning the molded mixture by additional heating or by being compression heated in a heated metal die. These conventional shaping methods suffer from various problems. The wet method is disadvantageous in that the metal die has a complicate structure because it is required to be provided with numerous fine through holes for permitting passage of water and steam, that the metal die for compression drying entails consumption of large amount of thermal energy because it is heated to a temperature of 200.degree. to 250.degree. C., that the operation of the metal die which exposes the metal die to compressive force of 15 to 50 kg/cm.sup.2 necessitates provision of a large compression device, and that the molding work takes up so much time as to impair the productivity of the method to a great extent. The dry method is also disadvantageous in that the process of fleece molding consumes a large volume of hot air kept at a temperature of about 200.degree. C., that similarly to the wet method, the operation of the metal die for complete burning uses up a large volume of thermal energy because the metal die is heated to a temperature of 200.degree. to 250.degree. C., and that the operation of the metal die which exposes the metal die to compressive force of 15 to 50 kg/cm.sup.2 necessitates provision of a large compression device.